[PATCH v2 2/3] Btrfs: don't build inode cache for orphan root

[Liu Bo <bo.li.liu@oracle.com>]

We check if we have orphan roots when mounting btrfs, but orphan roots
are those who are already dead and about to be freed, so don't start building
inode cache for them, otherwise we'll get an ugly crash.

Acked-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
 fs/btrfs/inode-map.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index f23b0df..b7fb1a8 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -141,7 +141,9 @@ static void start_caching(struct btrfs_root *root)
 	int ret;
 	u64 objectid;
 
-	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
+	/* Don't even start if this is an orphan root. */
+	if (!btrfs_test_opt(root, INODE_MAP_CACHE) ||
+	    btrfs_root_refs(&root->root_item) == 0)
 		return;
 
 	spin_lock(&root->cache_lock);
-- 
1.8.2.1